Removing rust with voltage plus acid
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Post Fiend
Joined: Apr 2002
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From: Central Kali
Removing rust with voltage plus acid
I did a pulley today using about a cup of aluminum wheel brightener in 2 gal of water. The current was 3 amps at about 10 volts. I ran it for 3 hours. The pulley was on the positive lead which is reversed from the washing soda setup.
The water turned a dark green. Is there a chemist in the house? The pulley was not completely rusted but had some thick rust in one of the groves.
Before and after pics: Edit- Bad link -Admin
The water turned a dark green. Is there a chemist in the house? The pulley was not completely rusted but had some thick rust in one of the groves.
Before and after pics: Edit- Bad link -Admin
Senior User
Joined: Nov 2003
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From: NW
Originally Posted by Mike W
I did a pulley today using about a cup of aluminum wheel brightener in 2 gal of water. The current was 3 amps at about 10 volts. I ran it for 3 hours. The pulley was on the positive lead which is reversed from the washing soda setup.
The water turned a dark green. Is there a chemist in the house? The pulley was not completely rusted but had some thick rust in one of the groves.
Before and after pics: http://img36.photobucket.com/albums...ic=DSC00290.jpg
The water turned a dark green. Is there a chemist in the house? The pulley was not completely rusted but had some thick rust in one of the groves.
Before and after pics: http://img36.photobucket.com/albums...ic=DSC00290.jpg
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Post Fiend
Joined: Apr 2002
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From: Central Kali
I fixed the pic I think. The positive lead goes to the pulley. The negative to a stainless tube.
http://img36.photobucket.com/albums/...t=DSC00307.jpg
http://img36.photobucket.com/albums/...t=DSC00307.jpg
Lead Driver
Joined: Nov 2000
Posts: 6,628
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From: Albuquerque
I've had a little experience with sacrificial anodes and plating. I suspect you are plating the stainless onto the part and the rust is going away in the process. But hey! I'm no expert or I wouldn't ask all those questions on this site.
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Posting Guru
Joined: Jul 2001
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From: Gainesville, FL
All,
There are some questions that need answering before we can explain these starnge going ons.
Since when did aluminum rust orange? This pulley is aluminum, isn't it? My guess is, that the surface discoloration was a stain not a corrosive coating?, Maybe?
Copper oxide will give off a green color when dissolved in an acidiic solution (i.e. sulfuric acid). Generally, when performing an anodic sacrifical process the sacrifical element is not the part interest. This means that aluminum should be less corrosive than stainless steel. I assure you, that is not the case in my world, I think? So, the electrons are driven to the aluminum via electrcical potential, but the cathode is more stable than the anode. Technically, this should not have worked? Did anyone notice the texture on the outside of the pulley's V-grooves? Was that texture present previous to the process? I'll bet, not? I'm getting lost in my own analysis.
I need an objective opinion on the sacrifical level of aluminum vs. SST? Aluminum should be the cathode, right?
Help me out,
KingFisher
There are some questions that need answering before we can explain these starnge going ons.
Since when did aluminum rust orange? This pulley is aluminum, isn't it? My guess is, that the surface discoloration was a stain not a corrosive coating?, Maybe?
Copper oxide will give off a green color when dissolved in an acidiic solution (i.e. sulfuric acid). Generally, when performing an anodic sacrifical process the sacrifical element is not the part interest. This means that aluminum should be less corrosive than stainless steel. I assure you, that is not the case in my world, I think? So, the electrons are driven to the aluminum via electrcical potential, but the cathode is more stable than the anode. Technically, this should not have worked? Did anyone notice the texture on the outside of the pulley's V-grooves? Was that texture present previous to the process? I'll bet, not? I'm getting lost in my own analysis.
I need an objective opinion on the sacrifical level of aluminum vs. SST? Aluminum should be the cathode, right?
Help me out,
KingFisher
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Lead Driver
Joined: Nov 2000
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From: Albuquerque
I'll bite
Alrighty then, I say we discuss it. I think I've learned more from arguing a point and hearing the replys than I did in high school.
I'm thinkin the pulley is steel.
A sacrificial anode system protects something from corosion. Zinc might be "sacrificed" to protect a steel tank. My question would be, where does the zinc go? Does it absorb the corrosion or does it plate onto the steel?
Plating might be a little bit different.
Where's my beer?
I'm thinkin the pulley is steel.
A sacrificial anode system protects something from corosion. Zinc might be "sacrificed" to protect a steel tank. My question would be, where does the zinc go? Does it absorb the corrosion or does it plate onto the steel?
Plating might be a little bit different.
Where's my beer?
Cargo Master
Joined: Jul 1999
Posts: 2,484
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From: New Egypt, New Jersey
I was thinking the pulley was steel also.
I work as a plater in a Hard Chrome plating shop. When we plate, The part itself is grounded (negative), and the annodes are hooked to positive. Before we start plating though, we always reverse the current to clean the parts first. Our sacrificial annodes (we call them drop annodes) are in place in the tank to attract the removed particles away from the parts.
Without seeing exactly how Mike actually had it all set up, it sounds like he did pretty much the same things as we do (except our removed particles are released into the Chromic acid bath). Our parts are all de-greased before we start, and look really clean to the naked eye before we begin, so we only run in reverse (Positive to part) for a very short time.
Sometimes we strip the parts first to remove existing chrome. We use a Hydrochloric acid/hot water mixture for this. The mix is as clear as water, but always turns green.
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Post Fiend
Joined: Apr 2002
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From: Central Kali
The pulley was steel. I need to get some more acid. The wheel brightener mentioned hydrofloric and one other in it. You can use washing soda instead but the acid is a lot faster. 
old and in the way
Joined: Jul 1997
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From: Lovely Hueytown Alabama
rust removal
do a google on electrolytic rust removal... there are volumes and dozens of web pages showing the process... it's not very complicated... but some of the processes are very ingenious..
john
john
Junior User
Joined: Apr 2004
Posts: 59
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From: Newport, North Carolina
Rust removal
I use this method of rust removal every day in my car port. Fill a container full enough to cover your article and add 1 tablespoon of baking powder per gallon of water used. Hook negative of battery charger to item to derust and the positive to a piece of metal (ferrous) Don't use aluminum. submerge both items. arrange the items in relation to each other until your charger reads about 4 amps. Leave for about 3 hours and you should be able to brush the rust off with very little effort.
Gene
Gene
